California legislators have introduced a bill to ban the possession, sale and distribution of shark fins used in soup.
If successful, the proposed ban will follow a similar measure enacted in Hawaii last year.
Oregon and Washington are also considering similar legislation.
Shark fins are used to create a luxury Chinese soup that can sell for as much as $US40 a bowl.
Supporters of the ban say shark finning is a cruel practice in which fishermen slice the shark's fin off while the animal is still alive and then throw the shark back in the sea to die.